The earlier sensing and control system shown and described in connection with FIGS. 17-19 of my prior U.S. Pat. No. 4,051,987 for releasing the stock gripping means at the end of a feed stroke operated satisfactorily under certain conditions but the mechanical system of a movable plunger, time delay spring, etc. had some disadvantages. The use of a given spring 253 in the system shown in said Patent could not accommodate a wide range of air pressure levels that might be used operating the feeder and the resultant variations in the length of the noted time delay for the auxiliary valve action resulted in the timing of the opening of the stock gripping means possibly being either premature or excessively delayed with respect to the completion of each feed stroke of the feed slide. Also the operative displacement of the sensing plunger 250 shown in said Patent had to commence at a point located at a considerable distance from the end of the feed stroke of the slide and this contributed to some degree to an uncertainty in the timing of the said stock release action. Further this prior system required close manufacturing tolerances for the spring 253 and little if any effective adjustment was possible after the arrangement was assembled.